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Old 09-29-2014, 06:32 PM   #21
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Sounds like you found the problem. You know what they say, "One bad apple can spoil the whole bunch." Hopefully the rest of the batteries can be revived.

Don't you have a Charles smart charger and shore power at your slip? If so, why not just leave the charger on whenever the boat's in the slip? The charger goes from bulk to absorption to float automatically. Then the batts are fully charged when you arrive. That's what I do with my house bank. I periodically resynchronize the monitor when I return to the boat to reset the monitor's 100% reference. My Xantrex will flash a "synchronize" message on the unit's screen when it's needed.
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Old 09-29-2014, 06:35 PM   #22
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I purchased a victron dual bank battery monitor and installed it earlier this year. ...
I don't trust myself to install electrical devices.
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Old 09-29-2014, 06:48 PM   #23
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Sounds like you found the problem. You know what they say, "One bad apple can spoil the whole bunch." Hopefully the rest of the batteries can be revived.

Don't you have a Charles smart charger and shore power at your slip? If so, why not just leave the charger on whenever the boat's in the slip? The charger goes from bulk to absorption to float automatically. Then the batts are fully charged when you arrive. That's what I do with my house bank. I periodically resynchronize the monitor when I return to the boat to reset the monitor's 100% reference. My Xantrex will flash a "synchronize" message on the unit's screen when it's needed.
Thanks Al, I'll know soon enough if the remaining batts are any good.

I always leave the Charles charger on when in the slip. We're currently on the Chesapeake full time mostly at anchorages until it gets too cold. We've been on the boat since late May relying on the SOC meter to charge the batteries. I think they've been habitually under charged.
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Old 09-29-2014, 06:50 PM   #24
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Thanks guys for all you input.
Yesterday I charged the batts for 3 hours to this point:
V = 13.62
I or current going in/out = +43
SOC = 100%
CE or consumed energy = 0
Battery charger amp gauge showed 50 amps


The CE at 0 means that all the amps used by the batteries since the last time the SOC was 100% was replaced ie batteries fully charged.
Of course they were not fully charged as the battery charger was still putting out 50 amps and the I was 43 amps.

So I disconnected the old battery from the house bank and checked it's voltage alone after a couple of hours, it was 11.22. Dead!

I removed this battery from the house bank and charged the remaining three new batteries to a point where the charger amp gauge showed 0 and the I on the battery monitor showed 3.8 amps. This only took about 1.5 hours. The batteries should be fully charged.
I re calibrated the monitor to a bank capacity of 300 AH which should account for the removed battery and reset the SOC manually to 100%

This morning I checked the monitor and this is what I got:
Voltage: 12.24 or about 50% SOC based on voltage alone
SOC 81%
CE 68 amps

It appears to me the battery monitor is simply using the consumed energy CE to derive the SOC. 68 AMPS used out of 300 available AMPS is 78%. Pretty close to the 81% the battery monitor is displaying.

But this is very wrong and doesn't take into account the voltage. Again I know to get the true SOC of a battery it must be unloaded for 24 hrs and a voltage reading at that time will give an accurate SOC. Since when using the boat it's not practical to unload for 24 hours, that's the real value in installing a battery monitor.

Lesson learned:

I relied on the SOC alone to monitor battery condition and this has probably caused me to damage or destroy 3 new batteries by habitually undercharging them.

Last May I checked the condition of the 2 year old battery by fully charging it and checking voltage 24 hours later and though I don't remember it's voltage it was satisfactory. I called the battery manufacturer and got the voltage readings vs SOC.

This of course depends on the battery monitor being installed correctly. Al you posted a site back last year that described in detail the correct installation method and along with the monitor manual I got it installed properly. The last battery negative terminal in line on the house bank is connected to the shunt. The other shut terminal is connected to engine ground and to a terminal block. Connected to the terminal block is the negative lead from a small inverter and the negative lead from the batt charger. There are no sucker leads from any negative terminals.

Just a note, the proper way to wire a bank is to have the negative ground be connected to the last battery in line and the charging current go to the first battery, ie charge and ground on opposite sides of the bank.
The 13.6 volt reading was not the batteries' resting voltage, but was instead the charging voltage. Your SOC meter knew that it was still charging, and also knew that more amperage had been put in than it thought had been taken out, so it displays a 100% SOC. It know it is wrong, but "dead reconning suggests that is where it is. Just like if you were dead reconning in the fog.

Once your batteries are fully charged, it should start to drop the indicated SOC as the batteries are used. Then it will measure how many amps go back in to get back to fully charged (as indicated by the batteries not taking more than a trickle charge), compare that to what was taken out and calculate an efficiency factor for its future use in calculating SOC.
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Old 09-29-2014, 07:20 PM   #25
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Originally Posted by timjet View Post
Thanks Al, I'll know soon enough if the remaining batts are any good.

I always leave the Charles charger on when in the slip. We're currently on the Chesapeake full time mostly at anchorages until it gets too cold. We've been on the boat since late May relying on the SOC meter to charge the batteries. I think they've been habitually under charged.
I didn't realize you were still on your trip! You're living the dream!! WTG.

Now I understand why you can't charge longer. Hopefully now without that bad battery, you'll see more normal bank behavior. Just charge as much as possible...maybe even a night or two in a marina for the electrical power might be worth it to know you're back at 100% for a resync.

I know, I know...that costs money and pilots prefer free!!
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Old 09-30-2014, 06:21 AM   #26
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>I think they've been habitually under charged.<

AGM die if overcharged perhaps the guesstimates put in the SOC meter charged at too high voltage , or for too long?

Some SOC meters learn the battery banks current capacity , and use that info to charge properly.
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Old 09-30-2014, 08:19 AM   #27
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Well probably the monitor didn't take into account the bad battery so it eas calculating a SOC based on a higher bank capacity. But what I don't understand is why the monitor didn't take into account the bank voltage when calculating the SOC. 10.8 volts and SOC of 80 %?????
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Old 09-30-2014, 08:52 AM   #28
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The 13.6 volt reading was not the batteries' resting voltage, but was instead the charging voltage. Your SOC meter knew that it was still charging, and also knew that more amperage had been put in than it thought had been taken out, so it displays a 100% SOC. It know it is wrong, but "dead reconning suggests that is where it is. Just like if you were dead reconning in the fog.

Once your batteries are fully charged, it should start to drop the indicated SOC as the batteries are used. Then it will measure how many amps go back in to get back to fully charged (as indicated by the batteries not taking more than a trickle charge), compare that to what was taken out and calculate an efficiency factor for its future use in calculating SOC.
Yes I will do that and have been the day or so since I determined there was a problem. Voltage is a good indicator of SOC but only after being unloaded for 24 hrs.
My problem is I have no idea what my bank capacity is. I have 3 105 AH batteries but their condition is unknown and I won't know until I completely recharge them, let them sit for 24 hrs and take voltage readings.

I can't do that right now as we are living on the boat. As Al suggested we will hook up to a marina probably in 3 days at Tangiers Island. They'll get a good complete charge but I still can't unhook them for 24 hrs. That will have to wait until we pull the boat out of the water the end of Oct.

Going forward I'll monitor voltage and recharge at 12.3 volts. I know the unloaded voltage should be higher so I should be safe operating it in this manner. Again without knowing the bank capacity the SOC is worthless.
Also monitoring the amps used and recharging those amps will work, but only if the batts in the bank are in excellant condition. IOW unless the batts are new they will require more amps in to get to fully charged than they use.

Then again the charge rate drops so low at the float stage that the only practical way to fully charge the batts is a day or two at a marina.

Perhaps I'm wrong though.
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Old 09-30-2014, 11:00 AM   #29
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Tim, I think, with a little help from your friends, you've really got yourself a bit upside down and inside out here, something I am an expert at doing to myself on any number of issues. Do you have the Calder book? Worth a re-read to understand the world of battery charging. Also worth a complete re-read is the manual for both your charger and your battery monitor. Time to forget the past and start fresh.
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Old 09-30-2014, 12:21 PM   #30
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Well probably the monitor didn't take into account the bad battery so it eas calculating a SOC based on a higher bank capacity. But what I don't understand is why the monitor didn't take into account the bank voltage when calculating the SOC. 10.8 volts and SOC of 80 %?????
The SOC only calculated the % of charge from the amps out vs. amps in. It's a straight count after synchronizing at a full charge and inputting the AH capacity of the bank...much like a digital fuel flow/fuel quantity counter. It doesn't use battery voltage to compute SOC. That's where the Balmar SmartGuage has an advantage over this type of SOC. The Balmar unit uses battery voltage and other parameters, but not current flow, to calculate SOC. It learns your battery bank and adjusts its capacity over time based upon the actual battery bank charge and discharge performance.

My hunch is that your monitor read the amps going into the bank, but the dead battery stored very few of those amps and also caused a loss in the other batteries connected to it. You saw an artificially high SOC due to that amp count that wasn't being captured. It's like having a leak in your fuel tank as you're counting your fuel volume going into the tank. You stop the pump at what you think should be full, but the fuel has leaked and continues to leak out the bottom. At least you've identified and fixed the leak.

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AGM die if overcharged perhaps the guesstimates put in the SOC meter charged at too high voltage , or for too long?

Some SOC meters learn the battery banks current capacity , and use that info to charge properly.
Not in this case. The Victron SOC is not connected in any way to Timjet's charger and has no influence on how the charger functions. It is only connected to the batteries. It just reads amps in and amps out and calculates the effect of that gain or loss on the AH capacity Tim has set for his bank.

Sounds like you're on the right path, Tim. Good to hear you can charge for a few days to top them off.

Do you plan to replace that bad battery with a new one to regain some capacity? If so, maybe putting one in early at the marina stay can give it a good charge to start off. Granted, if the others are low, they will bring the new guy down to their level over time, but at least you've regained some capacity with the addition of the new one.

BTW, are all your house batteries the same size and brand AGM?
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Old 09-30-2014, 12:32 PM   #31
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Tim- sounds like you are looking at determining SOC by at rest voltage. I don't think that is a good strategy. Better to look at charging volts and charging amps. When at bulk charge volts, which should be around 14.5, depending on your specific batts and their temp. When amps taper off and volts still 14.5, that is 100% charged. You can determine that without waiting a day.
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Old 09-30-2014, 01:00 PM   #32
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I consider mine 100% charged when the charger has been in float charge over night and the battery acceptance rate in around 1A.

Your bulk and absorption voltages might be around 14.5V, but your float will be much lower at around 13.6V. Check your charger manual for the voltages in the AGM profile. But if you stop charging at 14.5V with ample current still flowing into your battery bank, you're cutting it off before the 100% mark. The charger needs to switch to float to top off the battery.

Fortunately, AGM batteries have a much higher acceptance rate to a higher SOC than lead acid batteries. It might be that cutting it off early on an AGM bank would have less negative effect than doing the same on a lead-acid bank like mine.
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Old 09-30-2014, 01:09 PM   #33
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Some chargers, like my cheap POS, switch to float voltage based on a timer. Others switch to float when acceptance amps drop. This is better, but can be complicated if bank is being drawn from by fridge or other loads. The charger can't tell if the amps being provided are going to loads or to charging. In that sense, the timer might be the best option as long as the interval is carefully selected.

But you've got to get them up to 14.5 long enough to see the amps taper off.
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Old 10-01-2014, 01:11 AM   #34
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If you have a bad battery in parallel in a bank, it is just a big fat heavy resistor. It eats charging current and emits heat. Even worse once the chargers or alternators go away, it just eats the other batteries' energy.
Good to unhook the bank and look at each battery after charging if things are not behaving - as in one of the posts- this is a sure culprit finder.

Also note if you have a diode based isolator in use for house bank, it will drop .6v or so across it under current. So to get to 13.6 on the downhill side, need 14.2 on the uphill. I prefer auto combiners instead for little voltage drop from the alternators and even voltage to all banks.
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Old 10-01-2014, 08:54 AM   #35
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This is how I understand my 100 amp Charles charger works

The charger starts out in a bulk charge mode with voltage at 14.2 volts.

When the batteries near a "full charge" (full charge is not specified) the output current will decrease and the charger will enter a 4 hr timed absorption mode.

After 4 hours the output will drop to a float rate of 13.6 volts temperature compensated to slightly less if above 25 C or slightly more if below 25 C.

In practice while on the hook the charger never reaches the float rate due to the 4 hr timed absorption mode. This time of year with the OAT more comfortable we only run the genny to charge the batts.

What I have notice since removing the dead battery is the amp gauge on the charger and the amps being absorbed by the battery bank as indicated on the monitor drop quickly after about an hour of charge indicating the charger has gone to the absorption stage. Confirmed by the voltage dropping from 14.4 to 13.6.
That's when I turn the genny off.

So while on the hook, the batts will never get fully charged unless I leave the genny on for 5 hours or more which is not practical.

I don't know if this damages the AGM batteries as while on the hook they never are fully charged. Generally we get to a marina about once a week where they go through the full cycle and complete the absorption mode and enter the float mode.

Ski's comment about the refig running while charging is applicable. The fridge cycles and when on draws 7 amps. I don't know if this confuses the charger and it thus cycles to the absorption mode too early.

Any suggestions??

Perhaps running the genny all night once during that week on the hook is a good idea.
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Old 10-01-2014, 09:47 AM   #36
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I don't know if this confuses the charger and it thus cycles to the absorption mode too early.

Probably,

The answer could be a number methods.

Find an old RV converter and install it. If you want I have a $20.one.

These were made to not discharge the bats as demands like water pumps , fridges , lights ,etc operated.

The voltage was usually 13.2 ,so little watering was required , as there was almost no charging being done.

The tiny inland fish killers (300hp on a 18ft boat) use chargers that charge each battery alone.
So if 24 V (2 12v batts for trolling motor) is on one string and 12v on the other , no problem each gets 12v , would charge a 36 or 48v system, each batt sees only its 12V charger .

Not powerful so only for slip use , and some make RFI , so radio reception may suffer.

The newest smartest chargers shut down when the float is finished , saving water, and only turn back on when a set point is reached. Weather it could be set to not come on with the fridge ? Maybe
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Old 10-01-2014, 09:57 AM   #37
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I guess I missed it, what size, type, year and brand of inverter do you have? And the inverter is not with a built in charger - you have the Charles only?
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Old 10-01-2014, 10:48 AM   #38
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Tim- If you get amps to decay at 14.2, that last bit of charge from the timed 4hrs is probably not a huge part of your SOC. If you let it go through the full cycle once a week, that should be enough. I too would not bother running the gen for 4hrs to just finish the timed cycle.
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Old 10-01-2014, 11:58 AM   #39
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The SOC only calculated the % of charge from the amps out vs. amps in. It's a straight count after synchronizing at a full charge and inputting the AH capacity of the bank...much like a digital fuel flow/fuel quantity counter. It doesn't use battery voltage to compute SOC.
That's interesting, I thought the Victron was more sophisticated than just an amp hour meter. My Magnum took a number of factors, to calculate the batteries' charge efficiency and ultimately SOC. "At rest voltage" as Ski notes, (and Trojan and Magnum agree) is probably the most difficult to get a good reading (you have to decommission the bank for a fairly long period of time) and anything other than a true at rest reading is almost meaningless, since loads draw down voltage.

I had some of this same confusion myself when I was a newbie to a fairly complex system. Mr. Calder and Magnum set me straight.
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Old 10-01-2014, 12:22 PM   #40
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That's interesting, I thought the Victron was more sophisticated than just an amp hour meter.
This article does a pretty good job of explaining how the SOC meters function and their pitfalls. It also shows how the Balmar SmartGuage differs.

Smart Gauge Battery Monitoring Unit Photo Gallery by Compass Marine How To at pbase.com
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